1. Field of the Invention
The present invention relates to sensor devices. In particular the invention relates to new sensor for measuring a physiological signal from the skin. Such sensor typically comprises a substrate, a signal electrode, and means from transmitting a signal electrically. In addition, the invention relates to a method for manufacturing sensor, to a heart rate belt, and to apparel.
2. Description of Background Art
Traditional heart-rate meter heart rate bands and heart rate belts generally comprise a body made of plastic, on the surface of which there are two local electrodes to be placed against the chest. Electronics for transmitting a heart rate signal, typically to a wristop device, are built into the plastic body. Conductors from the electrodes to the electronics also run inside the body, which is generally attached against the chest with the aid of a flexible band.
Because plastic heart rate bands are relatively thick and can feel uncomfortable in use, heart rate belts and sensor utilizing textile materials in particular have been developed recently. One such is disclosed in WO publication 2005/032366. In the solution depicted in it, the electrodes and transmission conductors are surfaced with a conductive material directly in the textile material. The transmission conductors can afterwards be coated with an insulating material, so that only the electrodes remain in contact with the skin and the quality of the signal improves. However, the laminate then remains on the surface of the product at the conductors, so that the breathability of these locations is reduced and they may feel uncomfortable against the skin.
WO publication 2002/071935 (FI 110915) discloses a heart rate sensor, in which there are electrodes containing conductive fibres, at the ends of which there is a moisture-retaining layer to improve the electrical contact of the electrodes with the skin. This solution also has a problem with the placing of the signal transmission conductors relative to the fibre material, particularly with creating both reliable contacts with the electrodes for them and good electrical insulation.
WO publication 2003/082103 discloses a heart rate sensor, with electrodes made by moulding through a textile material. The electrical conductors can be added to the mould, in order to attach them securely to the electrode moulding. However, the electrical conductors remain loose of the surface of the fabric and liable to mechanical stresses acting on them. They can also be attached as part of the textile with the aid of thermo-compression, but then a powerful interference signal may connect to them from the skin through the fabric.
US publication 2005/0043641 discloses a device intended to measure heart rate, which can be detachably attached to a flexible band, or piece of apparel, with the aid of hooks in it. Though it can be attached to many different pieces of apparel, it does not eliminate the problem of discomfort when using traditional heart rate bands.